In particular, the corn-shelling machines of the prior art have a head fitted with a rotating roller, and preferably pairs of rollers counter-rotating in relation to rotation axes substantially horizontal to the ground or incident with the ground on the side of the direction of advancement of the machine.
The counter-rotating rollers are fitted with blades which pull the stalks of the plants downwards, picking the cobs.
The blades therefore rotate in a direction which pushes the stalk of the corn on the cob plant downwards, towards the ground; contemporarily the cobs, positioned on the upper part of the stalk, are forced to pass through a meatus delimited by pairs of sheller plates. The sheller plates interfere with the cobs, preventing them from falling through the meatus onto the ground. The cobs are then channelled towards an auger of the corn-shelling machine.
During the shelling phase of the cobs, the latter by coming into contact with the sheller plates inevitably lose corn grain or kernels which pass through the meatus identified by the sheller plates and fall to the ground. The loss of corn grain may be significant and notably reduce the harvest.
Once dropped onto the ground the kernels are no longer recovered, in part because this would be a time-consuming and expensive operation, and rot on the ground together with the stalk of the plant.